engleski

A quantum many body model for the embedded electron spin decoherence in organic solids

We present a generalized nuclear spin bath model for embedded electron spin decoherence in organic solids at low temperatures which takes the crucial influence from hindered methyl group rotation tunnelling into account. This new, quantum many body model, after resolved using the cluster correlation expansion (CCE) method, predicts the the decoherence profiles directly from the proton relative position and methyl group tunnelling splitting inputs. Decoherence profiles from this model explain adequately the influence from both strongly and weakly hindered methyl groups to embedded electron spin decoherence: The former accelerates decoherence by increasing the nearest neighbour nuclear spin coupling, while the latter enhances {; ; ; ; \em coherence}; ; ; ; through a novel confinement-like mechanism, in which the very strong nuclear spin coupling from the tunnelling splitting term suppresses those protons on the methyl rotors from participating in the bath dynamics. Both types of influences are successfully proven experimentally in representative organic polycrystalline matrices: methyl malonic acid for strongly hindered and acetamide for weakly hindered methyl groups, respectively.

Electron paramagnetic resonance spectroscopy ; Spin model ; Polycrystalline material ; Organic solids ; Spin-spin interactions ; Nuclear magnetic resonance

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